Hello again to the Mustang family, happy to have made it back to the Mustang life. Had an '05 but had to trade it for reasons of hauling more and larger 'stuff' because we were renovating a home and ultimately moving to it. We ordered a 2012 GT Premium, automatic, in the early part of May and we picked it up on June 20th. All I can say is WOW! We have about 1700 miles on it so far. What a difference from our '05.

I have come upon a problem for which I can't seem to find much in the way of a solution. Picture this . . . It’s warmed up to normal operating temperature. You’re driving in a civil manner (I know, trying to drive this machine in a civil manner is just plain hard to do!) in town where the speed limits are 25, 30 or 35. OK, you accelerate from a stop sign or traffic light with light throttle, it goes through 1st into second and then into 3rd where it just seems to almost shut down. I can see the RPM’s drop, then it catches back on and seems ok until the next stop. Another scenario . . . cruising at 30 or 35 and use mild acceleration to 40 or 45, there’s the same situation again, almost like it’s coasting and then catches. There’s no backfire or anything like that. Under harder acceleration, it seems like neither of these situations occur. It’s a little disconcerting. I’ve also noticed what seems like a slight ‘miss’ when running on cruise control at 55 or 65, when the computer calls for a little gas while going uphill.

As I mentioned, I’ve seen references to this same type of condition but no positive answer. Several have concluded it might be the Fuel Rail Pressure Sensor (FRPS) or possibly an EGR problem. I’m trying to follow the postings to see if anyone does come up with a solution but I'm not having much luck.

I won't be able to make a trip back to the dealership for a while since we're over in the valley (near Modesto) and the dealer is on the coast (Monterey) and I prefer to let them handle it since the car is only a month old.

I just wanted to throw this out there and see if there might be others on The Mustang Source who have or know of this type of problem?

Sorry for the long winded post but thanks for listening,
Ron

 

I have the 6mt ,which has the skip shift feature (first to fourth ) under light acceleratio. Could it be the car is just shifting to overdrive to save Mpgs? With 3.15 gears in the auto, it seems at 25 mph it so it could drop the rpm very low seeming like it was stalling or something. I could be way off, just a thought .

 

Auto does not have skip shift.

Sounds more like a throttle sensor or some form of electronics issue.

 

Looks like a nice GT you have on order.
Interesting thought, however, I doubt that's the cause since in all cases either I am, or the computer is still requesting throttle. I might have added also, that under heavier throttle I don't see the problem as frequently.

 

Please know I don't know anything! I can just guess.
I have an 11 Auto 5.0, mine does the same thing. Pretty much, I think? In the 9 mths I've owned it, I've only been like 8,200 miles. 1 thing I've noticed is that it was built for better MPG's. Just the way it accels while on cruise, not fast. Yeah, that's all I can think up. When I decel the trans downshifts! Never saw/heard that in an automatic.
I just guessed this was to conserve gas? Again, I'm as dumb as a rock so don't put faith into what I type!!

 

Sounds like that may be why I've seen some suggestions out there about the FRPS.

 

I have an auto with the FRPP tune. I don't really notice a problem like a "miss" but the transmission does upshift very early to improve mileage and having had 11 mustangs -- all but one of them manuals -- the auto does feel a little "soft" on light acceleration. At 30 mph it's probably already in 4th. Seems to work... I get 20 mpg around town and 25 mpg on the highway at 78 mph. Pretty impressive for ~400 hp.

 

Hi Ron and eliyarbrough,

This is Deysha with Ford Customer Service. Congrats on your new GT Ron, I know it’s an awesome ride!! I’d like to escalate this for you guys and help get it resolved so you can continue to enjoy it. Please make an appointment with your Ford dealer as soon as possible and PM me with your dealer, VIN, mileage, and contact info.

Deysha

 

Mine does the same thing. 1,000 miles. Picked it up a week ago.

I'll go to accelerate gently, and it seems to bog then take off. Really annoying.

 

Take it to the dealer and get it checked out and then get a cai and tune. It will turn your car into an animal.

 

Just dropped it off. I think I figured out what it is though. I think it has to do with a combination of where it idles at and the gear its in. For instance, if I come to a stop and there is a bump or slight incline in front of me, hitting the gas lightly will not generate enough powers to push the car up and over the incline. So I push more and then when it downshifts that is when it "takes off". I dropped it off anyway, so hopefully they'll check sensors etc...

Overall I love the car, but I definitely see a tune in my future. As it sits stock, it's a little to docile for me.

 

I've found it's very easy to drive this car "softly". Mash the pedal down harder and the power just keeps building! If it feels "too docile" most of the time, just use more throttle!

 

I've noticed that the problem occurs more readily around home where the normal temperatures are 90's and above. Once it gets really hot, almost any acceleration will cause the momentary stall or stutter. Even after slowing to make a turn off of a 45 MPH road onto a 25 MPH, apply throttle and it will stutter. I can pump the peddle or manually drop the auto from drive down to 3rd and it seems to smooth out.

Over on the peninsula where the normal temperatures are more in the 60's I don't have as much of a problem and then it's mainly well after the car is warmed up.

I have an appointment in the morning and my hope is that during one of these episodes it has thrown a code or two that they will be able to pick up on the computer, otherwise, because it's so much cooler here in the Monterey area, I probably won't be able to demonstrate the problem. We'll see though . . . I'll post any results.

Ron

 

Just got back from the dealer service. As I figured, there were no codes thrown and we couldn't get the car to duplicate the problem. It's very cool here this morning (58 degrees). In any case, there was an update for the PCM and the technician did update that module. We'll see what happens.

As mentioned, the really hot weather seemed to cause this problem more readily. If that continues then I will follow up with a dealership there in the Turlock/Modesto area.

Also, I could be causing this problem on my own according to: "21769 - Intermittent lack of power/surge/hesitation while driving - Brake over accelerator feature." BOA "Operators that rest a foot on the brake pedal when also applying the accelerator pedal may activate the BOA feature."

Being more used to a manual transmission I did develop a habit of using my left foot for brake and right for gas, I'm going to have to force myself to drive "one-footed" to see if I can avoid any self-caused problem.

I will post any followup information as it comes.

 

Thats the oddest left foot habit I've ever heard of from a manual transmission person. I only use my left for the clutch, my right is only for brake and throttle, making the transition from any manual or auto car seamless.

 

I believe 2 footed driving in NJ is illegal due to the mixed signals that can result from accelerating with the brake lights on. Its best to just keep that left down and planted.

 

Sounds to me like it's just shifting to a higher gear maybe too soon causing it to go very low in the RPM's. As a Guestimate I'd say it would be more pronounced on hot days is because the engine is pulling timing to account for the IAT's being hotter to prevent detonation. I say get a tune with the shift points defined differently. But again just my guess on the situation.

 

Um, let me see if I can clarify that. You're right about normally using the left foot clutch, right foot gas. What I was trying to indicate was that having driven that way for so long, I developed a bad habit after getting the first auto trans. I began using my left foot for the brake instead of taking my right foot off the gas and using it to brake. As a result I started leaning my left foot on the edge of the brake pedal. What seemed like little or no pressure on the brake peddle to me was apparently enough pressure to activate the BOA. It least that what it seems like so far, because I've managed to make myself keep that left foot off the brake and I haven't experienced the stutter or hesitation in the last few days. Hope that makes sense.

Ron

 

Deysha,

Just wanted to make a public Thank You for taking an interest and following this thread. It's nice to know that at least one large manufacturer is taking a proactive approach. I've learned that there's a whole lot more communication between Ford and its dealer's service departments than I had imagined. Here's hoping the results from this episode are positive.

Thanks again,
Ron

 

The problem was ME! I've had the chance to drive in hot weather and cool for several days now and have made sure that I've kept my left foot off of the brake pedal (unless actually stopping, of course ) and I have not experienced the stutter or hesitation. Apparently even resting the foot lightly on the pedal is enough to activate the BOA (brake over accelerator) feature indicated in the Ford bulletin. My appologies to my 2012 GT, Ford and TMF. Thankfully, the service department took the time to dig into the situation and found the bulletin. Apparently it isn't a well known feature. If anyone should be interested, let me know and I will post the complete text of the bulletin.